In most galaxies, highly energized gas associated with active black holes remains confined within several tens of parsecs of the central black hole, but in VV 340a the structure is larger by a factor of 30 or more. "In other galaxies, this type of highly energized gas is almost always confined to several tens of parsecs from a galaxy's black hole, and our discovery exceeds what is typically seen by a factor of 30 or more," said lead author Justin Kader, a UC Irvine postdoctoral researcher in physics and astronomy.
The team combined observations from multiple facilities, including radio images from the Karl G. Jansky Very Large Array near San Agustin, New Mexico, which show a pair of large-scale plasma jets emerging from either side of VV 340a. These jets arise as gas falling into the active supermassive black hole encounters extreme temperatures and magnetic fields, energizing material and ejecting it from the galaxy, and on larger scales the jets trace a helical pattern that signals jet precession, a gradual change in the jet's orientation over time.
"This is the first observation of a precessing kiloparsec-scale radio jet in a disk galaxy," said Kader. "To our knowledge, this is the first time we have seen a kiloparsec, or galactic-scale, precessing radio jet driving a massive coronal gas outflow." The researchers propose that as the jets propagate outward they interact with and push surrounding galactic material, heating it to form coronal line gas, a hot, highly ionized plasma normally confined to the compact inner region around active supermassive black holes and rarely observed extending deep into or beyond the host galaxy.
Kader estimated that the kinetic power carried by the outflowing coronal gas is equivalent to 10 quintillion hydrogen bombs detonating every second. "We found the most extended and coherent coronal gas structure to date," said senior co-author Vivian U, a former UC Irvine research astronomer now at Caltech's Infrared Processing and Analysis Center. "We expected JWST to open up the wavelength window where these tools for probing active supermassive black holes would be available to us, but we had not expected to see such highly collimated and extended emission in the first object we looked at. It was a nice surprise."
Observations from the Keck II Telescope in Hawaii revealed additional gas extending to about 15 kiloparsecs from the active black hole, which the authors interpret as cooler material marking the fossil record of past jet - galaxy interactions. This debris likely traces earlier episodes in which the jet expelled gas from the galaxy's inner regions, leaving behind large-scale structures that complement the currently observed coronal outflow.
Webb's infrared instruments, operating from a solar orbit about one million miles from Earth, were central to detecting the coronal line emission from VV 340a, a dusty system that obscures much of its interior from visible light observatories such as Keck. Infrared observations penetrate the dust, revealing the hot plasma flowing out of the galaxy, and the study concludes that the jet removes enough gas each year to equal the mass of 19 suns, substantially depleting the galaxy's reservoir of star-forming material.
"What it really is doing is significantly limiting the process of star formation in the galaxy by heating and removing star-forming gas," said Kader. A comparable jet has not been identified in the Milky Way, though Kader noted evidence that the Milky Way's central supermassive black hole experienced an active feeding event about two million years ago, which ancient Homo erectus observers on Earth might have seen in the night sky.
With the precessing jet and its associated coronal outflow now characterized in VV 340a, Kader and U plan to examine other galaxies for similar signatures to better understand how galaxies like the Milky Way evolve. "We are excited to continue exploring such never-before-seen phenomena at different physical scales of galaxies using observations from these state-of-the-art tools, and we can't wait to see what else we will find," U said. The project received funding from NASA and the National Science Foundation.
Research Report:A precessing jet from an active galactic nucleus drives gas outflow from a disk galaxy
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